Apparatus for making corrugated paperboard

ABSTRACT

A paperboard corrugating machine for forming board having two corrugated mediums joined at their flute tips without any intervening liner. The machine comprises a relatively heavy main frame (11) and a second frame (12) which is mounted for movement on the main frame. The main frame (11) carries two rolls (13 and 14) and the second frame (12) carries two rolls (15 and 16). Frame (12) can be locked into position and loaded against the upper roll (13), and the four rolls (13, 14, 15 and 16) lie in a single plane when the rolls are operational. With this construction, movement and twisting of the rolls (13 and 15) relative to each other, between which the fluted mediums are aligned flute tip to flute tip, is reduced.

This application is a continuation of PCT/AU97/00151 under 35 USC 371.

FIELD OF THE INVENTION

This invention relates to improvements in machinery for manufacturingcorrugated paperboard of the type in which two corrugated mediums arejoined at their flute tips without an intermediate flat sheet.

BACKGROUND OF THE INVENTION

Australian patents 609089 and 655076, which correspond to U.S. Pat. Nos.4,886,563 and 5,674,349 respectively, disclose machinery for forming acorrugated paperboard structure having flute tip to flute tip bonding inwhich two sets of corrugating rolls are aligned so that two corrugatedmediums are brought into tip to tip registration in the gap between thecentral two rolls and the combined mediums are then conveyed by anadjacent carrier roll to further downstream processing.

Patent 655076 identified that lack of rigidity in the support frame andin the corrugating rolls can lead to relative movement between thecorrugating rolls and consequently to misalignment of the flute tipsalong the length of a roll, that is transversely of the paperboard. Itattempted to alleviate the problem using end gears to control therelative position of the flute tips along the length of the two rolls.Misalignment of the flute tips in the finished board has a deleteriouseffect on the strength properties of the board.

BRIEF DESCRIPTION OF THE INVENTION

It is an object of this invention to provide an apparatus which reducesthe likelihood of misalignment occurring.

To this end the present invention provides apparatus for makingcorrugated paperboard in which two fluted mediums are joined at theflute tips without an intermediate liner in which two pairs ofcorrugating rolls are arranged so that the fluted mediums are broughttogether at their flute tips between the inner rolls of each pair theimprovement comprising the provision of one frame for all four rolls,with the second pair being on a second frame mounted on said one frameso that the second frame is moveable toward the inner roll of the firstpair of corrugating rolls.

In more detail the invention provides apparatus for making corrugatedpaperboard in which two corrugated mediums are bonded together at theirflute tips without any intermediate liner which apparatus includes

a) a frame for mounting two pairs of corrugating rolls

b) a first corrugating roll fixedly mounted on said frame

c) a second corrugating roll mounted on said frame and capable of beingpressed toward said first corrugating roll

d) a second frame mounted on said first frame on the side of said firstcorrugating roll remote from said second corrugating roll, said secondframe being capable of being moved toward and away from said firstcorrugating roll

e) a third corrugating roll fixedly mounted on said second frame

f) a fourth corrugating roll mounted on said second frame on the side ofsaid third roll remote from said first roll, said fourth roll beingcapable of being moved toward and away from said third roll

g) a locking mechanism for locking the second frame into position on thefirst frame so that a fixed gap is created between the first and thirdcorrugating rolls.

This frame arrangement contrasts with the frame used in the machinedescribed in patents 609089 and 655076. In those patents the frame wasin two parts with the first and second rolls and the carrier roll on oneframe, the third and fourth rolls on the second frame and the two framesbeing brought together to align the corrugations of the first and thirdrolls. This arrangement lacked rigidity particularly along the length ofthe aligned corrugations between the first and third rolls. The factthat the carrier roll was part of one frame made it cumbersome to move.

By having one frame for mounting all four corrugating rolls and mountingthe second pair of rolls on a second frame to form a cassette that ismountable on the first frame, movement and twisting of the first andthird corrugated rolls relative to each other is reduced.

It is preferred that the main frame be thicker than for conventionalcorrugating machines and a thickness of at least 200 mm is preferred.

BRIEF DESCRIPTION OF THE DRAWING

The drawing is a schematic representation of the invention showing themain rolls in their open or non operational positions.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The method and general form of the corrugating machine is similar tothat described in Australian patents 609089 and 655076.

The core of the apparatus is the arrangement of the two pairs ofcorrugating rolls. These are mounted on the main frame 11 shown indotted outline. A second frame 12 is mounted on the frame 11. The frame11 is made of plate steel of greater thickness than for conventionalcorrugators and the plates are spaced further apart than is conventionalto enable the use of wider bearings and to increase the columnarstiffness of the frame. The frame 11 is preferably formed of two 45 mmplates spaced 240 mm apart. In the machine direction the frame is widerat the bottom than at the top.

The first pair of corrugating rolls are rolls 13 and 14. Roll 13 isfixed to the main frame 11 and is the reference from which the locationsof the other rolls are determined. By fixing roll 13 in frame 11,twisting and other relative movement of roll 13 is restricted. Roll 14is loaded against roll 13 by hydraulic rams schematically shown as 21.

Rolls 15 and 16 are mounted cassette fashion on the second frame 12.Roll 15 is fixed in position within frame 12. The frame 12 is made ofsolid steel 200 mm thick. Roll 16 is loaded against roll 15 by hydraulicpressure provided preferably by a pair of hydraulic rams, schematicallyrepresented by ram 22. The frame 12 is loaded against roll 13 by a pairof hydraulic rams schematically represented by ram 23. When this hasbeen achieved frame 12 is locked into position by a pair of hydraulicrams as represented by 24 acting on a pair of over center togglemechanisms schematically represented as toggle 25 to lock roll 15 into afixed gap position relative to roll 13. When the frame 12 is locked intoposition on frame 11 the axes of the four rolls 13,14,15 and 16 lie inone plane. Preferably the four corrugating rolls are arranged in avertical array.

The other elements of the apparatus as shown in the drawing are thecarrier roll 31 the glue applicators 32 and 33 and the glue radiationcuring station 34. Carrier roll 31 is mounted independently of the frame11 as is glue applicator 33. The glue station 32 however is mounted onthe frame 11. In operation one paper web is fed over roll 14, betweenrolls 13 and 14 where it is corrugated and then over roll 13 betweenrolls 13 and 15. The second medium is fed over roll 16, between rolls 16and 15 where it is corrugated and then over roll 15 between rolls 15 and13. Glue is applied to the corrugated web on roll 13 by applicator 32 sothat the webs on rolls 13 and 15 contact at their flute tips as theypass through the gap between rolls 13 and 15. This gap between rolls 13and 15 is adjustable to cater for changes in the thickness of the paperwebs passing between the gap. The adjustment can be achieved usingtapered linear wedges against which the cassette is loaded. In order toachieve a fixed gap between rolls 13 and 15 and also exert a uniformpressure across the paper sheets the corrugating rolls are crowneddifferently to conventional corrugating rolls. Rolls 14 and 16 areprovided with positive cambers or crowns and rolls 13 and 15 areprovided with negative crowns or cambers whereas conventionalcorrugating rolls are all positively crowned. When the system is loadedthe gap between rolls 13 and 15 does in fact produce a roll profile thatis positive on both rolls. When the paper sheets are fed into the gapbetween rolls 13 and 15 the crowns or profiles flatten out to providethe uniform cross machine loading pressure. After leaving the gapbetween rolls 13 and 15, the joined webs then pass over the carrier roll31 past glue applicator 33 for a liner to be applied at a point [notshown] between applicator 33 and radiator 34. Exposure to infra redradiation at station 34 hastens curing of the glue to bond the mediumsto each other and the liner to the outer medium on carrier roll 31.

Because of the increased transverse rigidity of the rolls 13 and 15created by the frame 11 for roll 13 and by frame 12 set in frame 11 forroll 15 alignment of the flute tips transversely can be maintained athigher production speeds than with the machines disclosed in patents609089 and 655076.

The claims defining the invention are set out as follows:
 1. Apparatusfor making corrugated paperboard in which two corrugated mediums arebonded together at their flute tips without any intermediate liner whichapparatus includes(a) a first frame for mounting two pairs ofcorrugating rolls (b) a first corrugating roll fixedly mounted on saidfirst frame (c) a second corrugating roll mounted on said first frameand being movable toward and away from said first corrugating roll (d) asecond frame mounted on said first frame on a side of said firstcorrugating roll remote from said second corrugating roll, said secondframe being movable toward and away from said first corrugating roll (e)a third corrugating roll fixedly mounted on said second frame (f) afourth corrugating roll mounted on said second frame on a side of saidthird roll remote from said first roll, said fourth roll being movabletoward and away from said third roll (g) a locking mechanism for lockingthe second frame on the first frame so that a fixed gap is createdbetween the first and third corrugating rolls (h) the mounting of thesecond frame on said first frame reducing twisting and movement of saidfirst and third rolls relative to each other.
 2. Apparatus as claimed inclaim 1 wherein an over center toggle mechanism is used as the lockingmechanism.
 3. Apparatus as claimed in claim 1 wherein the first frame iswider in the machine direction at its base than at its top.
 4. Apparatusas claimed in claim 1 wherein when operational the four corrugatingrolls define respective axes which lie in a single plane.
 5. Apparatusas claimed in claim 1 wherein the first and third corrugating rolls arenegatively crowned.
 6. Apparatus as claimed in claim 5 wherein the innerroll of the first pair is fixedly mounted on the said one frame and theinner roll of the second pair is fixedly mounted on said second frame.7. Apparatus as claimed in claim 6 wherein the two inner rolls arenegatively crowned.
 8. Apparatus, for making corrugated paperboard inwhich two fluted mediums are joined at the flute tips without anintermediate liner, in which first and second pairs of corrugating rollsare arranged in line so that one roll from each pair form two innerrolls in the line of four and said fluted mediums are brought togetherat their flute tips between said inner rolls, the improvement comprisingthe provision of one frame for all four rolls, with the second pairbeing on a second frame mounted on said one frame so that the secondframe is moveable toward the inner roll of the first pair of corrugatingrolls.